Engineering could be largely contracted out as it will mostly based in UK or MOBs abroad
Let's not get too carried away with all this "engineering on the cheap" stuff hey (read the comments above on the C17 and thought the same thing).
MPA/MMA and C17, apples and oranges. MPA needs significant frontline engineering support in the shape of armourers and avionics to maintain and support a ton of weaponry and sensors.
When the RAF binned maritime about 3500 posts went at the same time. They were not all maritime related of course, but a hell of a lot of them were.
Even if you leverage every single "leaning" trick in the book, the RAF (and/or RN) are still going to have create a lot of new posts.
...and that costs a ton of money, as everybody should know.